LimitingClassLoader


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33  
34  package edu.rice.cs.util.classloader;
35  
36  import java.util.*;
37  
38  /** A class loader that does nothing but allow, at runtime, classes to be put on a list of "do not load" 
39   *  classes, which will be rejected from loading, even if they are available.
40   *  @version $Id: LimitingClassLoader.java 3901 2006-06-30 05:28:11Z rcartwright $
41   */
42  public class LimitingClassLoader extends ClassLoader   {
43    private List<String  > _restrictedList = new LinkedList<String  >();
44  
45    /** Creates a LimitingClassLoader.
46     *  @param parent Parent class loader, which is used to load all classes  not restricted from loading.
47     */
48    public LimitingClassLoader(ClassLoader   parent) { super(parent); }
49  
50    public void addToRestrictedList(String   name) { _restrictedList.add(name); }
51  
52    public void clearRestrictedList() { _restrictedList.clear(); }
53  
54    /** Overrides {@link ClassLoader#loadClass(String,boolean)} to reject classes whose names are on the 
55     *  restricted list.
56     *  @param name Name of class to load
57     *  @param resolve If true then resolve the class
58     *  @return {@link Class} object for the loaded class
59     *  @throws ClassNotFoundException if name is on the restricted list, or if the parent class loader couldn't
60     *          find the class.
61     */
62    protected Class  <?> loadClass(String   name, boolean resolve)
63      throws ClassNotFoundException  
64    {
65      ListIterator itor = _restrictedList.listIterator();
66  
67      while (itor.hasNext()) {
68        String   current = (String  ) itor.next();
69        if (current.equals(name)) {
70          throw new ClassNotFoundException  ("Class " + name +
71                                           " is on the restricted list.");
72        }
73      }
74  
75      // If we got here, the class was not restricted.
76      Class  <?> clazz = getParent().loadClass(name);
77  
78      // Because we couldn't call the protected loadClass(String,boolean)
79      // on the parent, here we handle resolution if needed.
80      if (resolve) {
81        resolveClass(clazz);
82      }
83  
84      return clazz;
85    }
86  }
87
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